Hey @MRT,
As you found, the V2 endpoint /v2/projects/{project_id}/customers/{customer_id}/subscriptions is only for RC Billing and Web SDK right now - a version of this endpoint that works for all customers is currently in beta but it is not public yet.
The V1 endpoint /v1/subscribers/{app_user_id} will continue to be available and we have no plans to discontinue or deprecate it at this time!
I would recommend you add to the v2 documentation “ONLY FOR WEB SUBSCRIPTIONS USING REVENUECAT BILLING” note for that you can still use v1 to get everything.
As a potential new user evaluating the service who considers that a necessary feature I was almost dissuaded into thinking it’s not currently supported (even though it is by v1) - most API upgrades don’t lose critical functionality so I only thought to check the v2 at first to see what’s offered.